Third generation partnership project (3GPP) mobile communication systems based on a wideband code division multiple access (WCDMA) radio access technique are widely spread all over the world. High-speed downlink packet access (HSDPA) that can be defined as a first evolutionary stage of WCDMA provides 3GPP with wireless access technique that is highly competitive in the mid-term future. However, since requirements and expectations of users and service providers are continuously increased and developments of competing radio access techniques are continuously in progress, new technical evolutions in 3GPP are required to secure competitiveness in the future. Reduction of cost per bit, increase of service availability, flexible use of frequency bands, simple structure and open interface, proper power consumption of a user equipment, and the like are defined as requirements.
Paging refers to an action in which a network pages one or more user equipments so as to perform a specific purpose. Paging has a function of saving power of a user equipment by preventing the user equipment from waking up except for necessary cases as well as a basic function of allowing a network to find a location a user equipment. When a user equipment receives a paging message is received from a network in a sleep mode, the user equipment wakes up and then performs an action requested by the network.
In order for the user equipment, which is in the sleep mode, to notice arrival of paging, the user equipment wakes up periodically and check whether paging information is arrived. What a user equipment does not always wake up, but wakes up periodically is generally called Discontinuous Reception (hereinafter, referred to as “DRX”).
When receiving a paging message, a user equipment can perform DRX to reduce power consumption. A network configures several paging occasions during a paging DRX cycle. A specific user equipment can receive a paging message at a specific paging occasion. The user equipment does not receive the paging message at times other than the specific paging occasion. One paging occasion may correspond to one TTI (Transmission Time Interval).
In general, the size of a paging message to call (or page) one user equipment is fixed. There is a need for a method of paging a user equipment efficiently depending on the size of a paging message by employing a paging occasion.